The invention relates to a twin-screw machine, the screws of which can rotate in the same direction, for melting, mixing, dispersing, shearing and imparting energy, consisting of a housing which has a figure-eight cross-section and contains circular eccentrically arranged kneading discs which can be rotated.
Circular eccentric discs are known wherein the discs are displaced relative to one another in a spiral staircase fashion and are fixed to shafts running along the two axes of the circular sections of the housing, the eccentric discs almost touching one another and the wall of the housing along a wavy line.
The disadvantages of these discs is that, during conveying and melting, solid polymers are gripped by the eccentric discs, so that the disc can be subjected to loads directed to one side, which can lead both to a high content of abraded metal in the material and to severe wear on the machine. This is in contrast to the balanced forces which, as a result of self-centering by radial forces uniformly distributed around the periphery, otherwise arise in twin-screw machines with screws which can rotate in the same direction. Furthermore, in the plastic state, the processed material escapes axially from the squeezing effect. Most of the material which partly or completely fills up the space is thereby withdrawn from the shearing stress actually intended, while a small portion is overstressed.